One problem related to transmission not engage has been reported for the 2006 Dodge Ram 3500. The most recently reported issues are listed below.
Intermittent problem. Truck (2006, 3500 quad cab dually) sometimes acts like the brakes are not releasing or the transmission is not engaging for a few seconds when accelerating from a complete stop. Took it to a local dealer (orange park Dodge in jacksonville, FL. Who could not replicate the problem. I had someone tell me that they knew someone in la. That had the same problem and their dealer knew exactly what was wrong and affected repairs. Unfortunately I don't remember who that was.